Monitor Jitter Fixed!


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Posted by Tom A. on 26, 2000 at 9:14 PM:

I fixed it! I discharged the tube but it never ever made a popping sound but I made sure I touched the anode wires with the screwdriver and no pop. I couldn't figure out how to disconnect the monitor pcb from the tube so I just took the unit out in one piece...tube and all. I soldered a few joints that I thought looked possibly bad but in retrospect, they were just flux marks. What I should have done was buy a magnifying glass and inspect each solder joint carefully. No, that would have been too easy. ;-)

After I "fixed" the couple "suspect" joints I fired it up and it still didn't work. I was a bit discouraged and quit for the evening (Friday). Saturday I went to a local TV/VCR repair place and asked them if they would work on it, they weren't interested in looking at it unless it was a TV or VCR. I called an arcade shop and he said he could look at it if I had the monitor schematic...well I don't.

So, I figured what do I have to lose except a lot of time? I refluxed each and every solder joint (except the ones that had no components attached) and although it took most of Saturday, I did it and when I fired it up nothing caught on fire and the vertical jitter is gone. Toward the end of the soldering process I did see what looked to be a small (very small) crack on one of the solder joints for a capacitor. I expect this was the culprit but I decided to just finish 'em all. That's why I think I should have bought a magnifying glass and inspected better.

Oh well, it's done and works! Now, the only problem I have with the monitor is a very, very slight horizontal swaying or jitter if you will. I believe I have always had this but it was inconsequential compared to the vertical jitter. I need to see if it does it when it's hot/cold etc. but for now I'll just lay low for awhile and enjoy some games.

Anyone have an idea what may be causing my slight horizontal jitter. I wonder if it could be the cap's?

-Tom A.

: I have a generic JAMMA cabinet that was built around 1996, maybe 1997. It is a Capcom Impress Multi Utility Cabinet that has a 29" Toshiba monitor in it. I have an owner's manual for it but it is in Japanese.

: I interface the computer to the cabinet with a typical PC2JAMMA fingerboard setup. I left the JAMMA harness intact so that I can hookup JAMMA boards if I so choose.

: When I have the PC hooked up to the JAMMA connector, the picture looks perfect for anywhere from 5 minutes to an 1 hour. At that time, the picture will jump just a little or the bottom part of the image will basically go in and out. It's hard to describe exactly but it acts like there is a loose wire. When I disconnect the PC and connect a SFII JAMMA board, the problems are the same but they don't seem quite as severe.

: After the jittering starts it will usually last for 15-30 minutes than it usually goes away. However, sometimes it does come back, I notice this more when I'm a little rough on the control panel...usally when playing with 2 players.

: Is it normal for the picture to jitter when the unit is lightly tapped? When I first turn the unit on I can tap on the control panel, side of the monitor or in the bottom compartment of the cabinet (directly below the monitor pcb) and the picture will not jump or jitter unless it is hit fairly hard. However, once the unit has warmed up for 30 minutes or so, I can lightly tap the control panel, side, or especially the bottom compartment just below the monitor PCB and the picture will jump or jitter. Sometimes after tapping it, the picture will straighten back up or sometimes it will jitter a little more. Like I said it acts like there is a loose wire.

: Now I have no experience whatsoever with electronics other than knowing how to use a soldering iron so I was hoping that this little bit of information I have provided could be used to tell me whether there is a possible component going bad on my monitor pcb or whether it is strictly a loose wire somewhere.

: I thought maybe it was the molex connector that connects the video signal wires from the JAMMA harness in the bottom of the cabinet to the monitor PCB in the monitor section of the cabinet but when I eliminated the molex connector and soldered the wires together, the problem still exists.

: Now the only video input signals that aren't soldered is the video connector to the monitor pcb. I didn't think it was a good idea to try to solder the wires directly to the monitor pcb pins.

: Maybe I should try to tighten the connector pins that connect the video signals to the monitor pcb? I'm a little leary of doing this because I'm afraid I may screw up the connectors but if it would eliminate the problem, I would be willing to give it a try.

: Any ideas or suggestions would be appreciated.

: -Tom A.




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